A method, apparatus, and computer instructions for determining validity of and updating a microcode image. Responsive to initiation of an update process, a first validity indicator is checked to determine whether a first microcode image in the memory is valid. In response to the first microcode image being valid, a second validity indicator is set indies, to indicate that a second microcode image is invalid, and the update process is allowed to update the second microcode image to form an updated microcode image. A determination is made as to whether the updated microcode image is valid. The second validity indicator is set to indicate that the updated microcode is valid if the updated image is valid. The second validity indicator is checked during booting of a data processing system. If the second validity indicator is valid, the updated microcode will be loaded.